Efficient solid dielectric electrochemical polishing with minimal electrolyte consumption and reusable conductive media

Abstract

Electrochemical polishing finds wide application across various industries, including manufacturing, biomedicine, and semiconductors. However, this technology requires substantial water usage and results in environmental pollution due to the generation of waste electrolytes containing highly corrosive acids and heavy metal ions. Herein, we propose an electrochemical polishing method (SDEP) that employs solid dielectrics consisting of macroreticular ion exchange resin (MIER) solid particles and phosphoric acid electrolyte as an alternative to traditional liquid conductive media. Maintaining a polishing current of 0.4–0.5 A requires only an electrolyte consumption of 10–20 mL/h, leading to a more than 65% reduction in electrolyte usage compared to liquid electrochemical polishing. Meanwhile, this method can be applied to polish additively manufactured metal parts with an initial roughness Ra>10 μm. The achievable surface finish features Ra = 0.778 ± 0.078 μm, Rq = 0.960 ± 0.121 μm, and Rz = 4.175 ± 1.111 μm after 1-h polishing, with a material removal rate of 0.15–0.19 mm3/min. The improvement of Ra, Rq, and Rz are 92.3%, 92.1%, and 92.0%, respectively. With the EDS and XPS analysis, rod-shaped by-products adhering to the surface of MIER particles generated during the SDEP process are confirmed as Fe3+, PO43−, and PO3−. Furthermore, the MIER particles can be reused after cleaning, exhibiting polishing performance comparable to fresh MIER. This method reduces the use of electrolytes at the source of electropolishing, and MIER particles can be recycled, pointing towards the development of eco-friendly electrochemical polishing.